As discuss on github I continu here.
I tried to follow your recommandation
A simple way is to make two branches from master, then undo all the commits in master so that it is back at its original state. You can then edit each of the branches to remove the stuff that should not be there. Also, look at "squashing commits", so that there is only one commit in each branch.
I finaly could create clean master and 2 branch.
So I could submit new PR.
But when i undo commit this close the PR?
Can I continue it, from another branch?